Immunodetection of Pectic Epitopes, Arabinogalactan Proteins, and Extensins in Mucilage Cells from the Ovules of Pilosella officinarum Vaill. and Taraxacum officinale Agg. (Asteraceae).

Bartosz J Płachno,Małgorzata Kapusta,Piotr Świątek,Janusz Kocki,Piotr Stolarczyk

doi:10.3390/ijms21249642

Abstract

The main aim of this study was to compare the cytological difference between ovular mucilage cells in two Asteraceae species—Pilosella officinarum and Taraxacum officinale—in order to determine whether pectic epitopes, arabinogalactan proteins, or extensins are present. The immunocytochemical technique was used. Both the Taracacum and Pilosella genera have been used recently as models for understanding the mechanisms of apomixis. Knowledge of the presence of signal molecules (pectic epitopes, arabinogalactan proteins, and extensins) can help better understand the developmental processes in these plants during seed growth. The results showed that in Pilosella officinarum, there was an accumulation of pectins in the mucilage, including both weakly and highly esterified pectins, which was in contrast to the mucilage of Taraxacum officinale, which had low amounts of these pectins. However, Taraxacum protoplasts of mucilage cells were rich in weakly methyl-esterified pectins. While the mucilage contained arabinogalactan proteins in both of the studied species, the types of arabinogalactan proteins were different. In both of the studied species, extensins were recorded in the transmitting tissues. Arabinogalactan proteins as well as weakly and highly esterified pectins and extensins occurred in close proximity to calcium oxalate crystals in both Taraxacum and Pilosella cells.

Highlights

There are two main types of mucilage cells in plant seeds
Pectins In Taraxacum and Pilosella, weakly methyl-esterified pectins, homogalacturonans labeled with JIM5, occurred in the cell walls of different ovule tissue cells (Figure 1C,E)
In the mucilage cells of Taraxacum, these pectins occurred in the cell walls and protoplasts, but there was less intense labeling in the mucilage (Figure 1C,D)

Summary

Introduction

There are two main types of mucilage cells in plant seeds. The second type is mucilage cells that produce and collect mucilage inside a cell (at least during part of the cell life). The first subtype is epidermal mucilage cells of the seeds, e.g., Plantago [6,7,8], members of the Brassicaceae family including the model plant species Arabidopsis thaliana (e.g., [9,10,11,12]), Sapindaceae [13], fruits such as Asteraceae cypsela [14,15], and Asteraceae cypsela epidermal trichomes [16]. The third subtype is mucilage cells in which the mucilage accumulates between the cytoplasm and the central vacuole into a specialized cavity, e.g., Araucaria angustifoli [20,21]. It should be noted that mucilage can be secreted by ducts and cavities [22]

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Discussion

Conclusion